Download Document 10099561

Smithycroft Secondary
National 5 Chemistry
Unit 3: Section 10 – Properties of Plastics
Learning Statement
Most plastics and synthetic fibres are made from crude oil.
 Synthetic means that the fibre has been made by scientists and is not
naturally occurring.
 Both natural and synthetic fibres are examples of polymers.
There are advantages and disadvantages of using natural or synthetic materials.
Some plastics release toxic gases when they are burned.
A biodegradable plastic is one that can be broken down by organisms such as
bacteria.
There are 2 types of plastic: thermoplastic and thermosetting.
 Thermoplastics melt on heating, as their polymer chains are not crosslinked.
 Thermosetting plastics keep their shape on heating, as their chains are
cross-linked.
Polymers are large molecules made from smaller molecules called monomers.
There are 2 types of polymerisation:
 Addition
 Condensation
Addition Polymerisation
In addition polymerisation small unsaturated monomers containing a C=C undergo
addition reactions to form a saturated polymer.
e.g.
The polymer name starts with poly and then has the name of the monomer in
brackets, for example ethene monomers polymerise to make poly(ethene).
Condensation Polymerisation
In condensation polymerisation monomers with functional groups at each end of
R A G
the molecule undergo condensation reactions to form a polymer and water.
Making Polyester
Polyesters are chains of polymers that contain an ester functional group. They
are made from a carboxylic acid monomer and an alcohol monomer.
Creative and Smart Materials Made from Polymers
 Kevlar is made by condensation polymerisation and is used in bullet proof
vests. It is a very strong fibre but is lighter than any other material with
the same strength.
 Polyvinyl Alcohol (PVA) is a soluble plastic that can be used to make
laundry bags.
 Poly(acrylate) is a hydrogel that has special water absorbing properties
which allows hydrogels to be used in a variety of applications such as
nappies, contact lenses and as medical bandages.
 Colour changing plastics can be used in food packaging to let consumers
know the condition of food inside.
 Conductive plastics are currently being researched which allow the
development of flexible touch screens and e-paper in the near future.